In related art, a display panel using organic electro luminescence (EL) is coupled via a flexible board to a printed board that supplies a power source and a signal to a drive circuit of the display panel. For instance, Japanese Unexamined Patent Application Publication No. 8-181413 discloses a printed board in which when formation of wiring on only one side of a base material is difficult due to a high packaging density of electronic components, a wiring pattern is formed using both front and back sides of the base material.